Abstract

Newpark Environmental Services has developed a study program to assess cost-effective technologies and strategies for the treatment of hydrocarbon contaminated solids. Enhanced bioremediation and soil washing through the use of surfactants are hypothesized to be key remediation strategies. Newpark Environmental Services developed test systems to evaluate the efficiency of commercial bioremediation agents (CBA) intended for application to hydrocarbon contaminated soils. The accelerated treatability tests are decision - making framework to evaluate the potential full-scale and cost-effective waste treatment options. This paper presents tests designed for assessing the feasibility of bioremediation and soil washing and some preliminary results on some soils that were evaluated.

Introduction

Surfactants (surface active agents) are a class of natural and synthetic chemicals whose ability to promote the wetting, solubilization and emulsification of various types of organic chemicals have found widespread application. These properties make surfactants of possible use in the treatment of certain organic fractions in waste deposits. Used in bioremediation or soil washing treatment techniques, surfactants may offer a means of improving the removal efficiency.

Recent world researches are focused on surfactant enhanced bioremediation. The application of surfactants can improve bioremediation in two ways: by increasing contaminant mobility and solubility, and to speed the rate of biodegradation of contaminants in soil/waste. Surfactants increase contaminant removal in two ways. The first is by increasing the apparent solubility of the contaminant in water, which improves the mass removal per pore volume. The second is by reducing interfacial tension. Cationic surfactants have been shown to improve the capacity of soil to sorb hydrophobic organic contaminants such as polyaromatic hydrocarbons. Other research suggests that surfactants may be useful for enhancing in situ biodegradation of hydrophobic pollutants at low surfactant concentrations. Laboratory treatability studies are recommended prior to embarking on large-scale field treatments. Upstream-contaminated materials are nearly always of unknown composition, and often little is known of the history of specific materials. The purposes in doing treatability and enhancement studies are to:

  • Identify the suitability of specific contaminated materials as candidates for bioremediation;

  • Identify serious processing problems;

  • Determine best or most expedient environmental conditions;

  • Predict quantity of hydrocarbon residuals;

  • Predict treatment duration.

The second technique on which we focused on is washing with using surfactants. Solids washing systems that incorporate multiple removal techniques offer the greatest promise for application to soils contaminated with a wide variety of pollutants such as organic contaminants. Commercialization of the process, however, is not yet extensive. Solids washing is an environmentally safe method for recycling hydrocarbon contaminated soil. This is the EPA approved form of soil remediation. An initial step in the soil wash process is to fully disperse the contaminated soil in a water/surfactant ‘bath’. The combined powerful mechanical action and washing process serve to break the clay matrix apart, thus allowing the surfactant to strip the hydrocarbon contaminants from the soil particles.

In general, surfactants are used to both increases the total aqueous solubility of some hydrocarbons such that the dissolution process is accelerated and to decrease NAPL-water interfacial tension such that physical mobiliza

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